/**
 * Copyright (c) 2024 Hunan OpenValley Digital Industry Development Co., Ltd.
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
#include "GPUImageSaturationFilter.h"
#include <GLES3/gl3.h>

const std::string GPUImageSaturationFilter::SATURATION_FRAGMENT_SHADER = R"(
    #extension GL_OES_EGL_image_external : require
    varying highp vec2 textureCoordinate;
    
    uniform samplerExternalOES inputImageTexture;
    uniform lowp float saturation;
    
    // Values from "Graphics Shaders: Theory and Practice" by Bailey and Cunningham
    const mediump vec3 luminanceWeighting = vec3(0.2125, 0.7154, 0.0721);
    
    void main()
    {
        lowp vec4 textureColor = texture2D(inputImageTexture, textureCoordinate);
        lowp float luminance = dot(textureColor.rgb, luminanceWeighting);
        lowp vec3 greyScaleColor = vec3(luminance);
        
        gl_FragColor = vec4(mix(greyScaleColor, textureColor.rgb, saturation), textureColor.w);
    }
)";

GPUImageSaturationFilter::GPUImageSaturationFilter() : saturation(1.0f) {}

GPUImageSaturationFilter::GPUImageSaturationFilter(const float saturationVal)
    : GPUImageFilter(NO_FILTER_VERTEX_SHADER, SATURATION_FRAGMENT_SHADER)
{
    saturation = saturationVal;
}

void GPUImageSaturationFilter::onInit()
{
    GPUImageFilter::onInit();
    saturationLocation = glGetUniformLocation(getProgram(), "saturation");
}

void GPUImageSaturationFilter::onInitialized()
{
    GPUImageFilter::onInitialized();
    setSaturation(saturation);
}

void GPUImageSaturationFilter::setSaturation(const float saturationVal)
{
    saturation = saturationVal;
    setFloat(saturationLocation, saturation);
}
